A method of separating carrier-free strontium-90 and yttrium-90 with stannic phosphate impregnated paper was described. Asccnding chromatography was used with ammonium nitrate, nitric acid, or hydrochloric acid as the eluent. The relationship beaween the R_f values of the Sr⁹⁰ and Y⁹⁰ and the concentration of the eluent was studied. The R_f values of Sr⁹⁰ increased with increasing concentration of eluent, as the concentration of eluent varied from 0.1 to 2.0 M. A clear separation of Sr⁹⁰ and Y⁹⁰ was achicvcd within 1 1/2 hour. The effects of methanol, ethanol, and acetone on the R_f values were also studied.